As a result of recent increases in certain contagious diseases such as the Acquired Immune Deficiency Syndrome (AIDS), the number of cases reported where a human being has been inadvertently pricked with the needle of a syringe is growing at an alarming rate. With the current increase in these infectious diseases which may be transmitted by a contaminated syringe, this fact has caused a great concern in the medical community and other related professions not only for the health and welfare of nurses, physicians, and patients alike, but also a concern for the health and welfare of people within the illegal drug community.
Most standard types of syringes are designed so that the needle portion of the syringe is permanently in place in an extended position at the end of the syringe and there protected by a cap which is to be removed at the time the syringe is used either in the home or in hospital applications. However, an obvious disadvantage with this type of syringe construction and design (which may indeed represent the lowest cost of syringe construction) is that during the syringe handling and use by the hospital personnel and patients alike there is a relatively high degree of needle exposure to humans per unit of time that the syringe is in actual handling or use. In addition, these fixed-needle types of syringes have been known to cause needle puncture through a wall of a protective cap being replaced thereon and stick the person handling the syringe.
To reduce this human exposure time to the exposed needle, certain types of retractable-needle type syringes have been developed wherein mechanisms are provided within the syringe for withdrawing the needle to a protected and shielded position within the housing of the syringe after the syringe is actually used for giving an injection to a patient. Examples of such a retractable-needle type syringe are disclosed in U.S. Pat. No. 4,790,822 issued to Haining and in U.S. Pat. No. 4,838,869 issued to Allard, both incorporated herein by reference. However, these retractable-needle types of syringes have nevertheless failed to provide a minimum of human exposure to the needle of the syringe per unit of time when the syringe is in actual use. Furthermore, these retractable-needle type syringes have not been designed such that the syringe is disabled after use. This of course leaves open the possibility that the syringe may be retrofitted and subsequently used in such a manner to transmit an infectious disease.
Thus, these prior art devices do not minimize as completely as possible all kinds of accidental needle contacts by humans and the possible contamination of and disease contraction to a human who is inadvertently pricked by an exposed needle. With the current unfortunate increase of many contagious and infectious diseases, the desirability of reducing to an absolute minimum this quotient of human exposure-to-needle time per unit of time when a syringe is being handled and operated while simultaneously providing a totally disabling capability to the syringe is manifest.